This invention relates to electromagnetic couplings, and more particularly to electromagnetic couplings utilizing magnetizable particles for transmitting torque between relatively rotatable rotary members.
Electromagnetic couplings are known as being usable as brakes, clutches and the like. U.S. Pat. No. 2,804,955 discloses one type of electromagnetic coupling in which a driven member including a magnetizing coil is surrounded by a driving member with an annular air gap provided therebetween for containing therein magnetizable torque transmitting particles. U.S. Pat. No. 3,249,184 discloses another type of elecgromagnetic coupling in which a relatively thin drum portion is inserted within an air gap formed between an outer driving rotor member and an inner stationary field structure including a field winding. This patent also discloses an arrangement for mounting the drive member to the input shaft.
In conventional electromagnetic couplings including those disclosed in the above mentioned patents, the magnetizable particles or the torque transmitting medium within the air gap between relatively rotatable members are subject to a heating problem when there is a relative rotary motion between the rotatable members because of the slippage or the friction between each of the magnetizable particles contained in the air gap. If this heating of the particles is not efficiently removed, the temperature of the particles may raise to such an extent that the particles weld to each other and their magnetic properties change, decreasing the reliability of the electromagnetic coupling.